Residue removal during semiconductor device formation

ABSTRACT

In an example, a method may include removing a material from a structure to form an opening in the structure, exposing a residue, resulting from removing the material, to an alcohol gas to form a volatile compound, and removing the volatile compound by vaporization. The structure may be used in semiconductor devices, such as memory devices.

PRIORITY INFORMATION

This application is a Divisional of U.S. application Ser. No.15/847,587, filed on Dec. 19, 2017, the contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to semiconductor processing,and, more particularly, to residue removal (e.g., during semiconductorprocessing, such as memory device processing).

BACKGROUND

Semiconductor processing (e.g., fabrication) can be used to formsemiconductor devices, such as integrated circuits, memory devices,microelectromechanical devices (MEMS), etc.

Examples of memory devices that can be formed by semiconductorprocessing include, but are not limited to, volatile memory (e.g., thatcan require power to maintain its data), such as random-access memory(RAM), dynamic random access memory (DRAM), synchronous dynamic randomaccess memory (SDRAM), among others, and non-volatile memory (e.g., thatcan provide persistent data by retaining stored data when not powered),such as NAND flash memory, NOR flash memory, read only memory (ROM),electrically erasable programmable ROM (EEPROM), erasable programmableROM (EPROM, among others.

Semiconductor processing can involve forming features (e.g., patterns)on and/or in a substrate, such as a semiconductor (e.g., of silicon),that may be referred to as a wafer. In some examples, one or morematerials, such as silicon-based materials (e.g., silicon oxide (SiO),silicon nitride (SiN), tetraethyl orthosilicate (TEOS) and/orpolysilicon, among others) may be formed on the substrate. For instance,a deposition process, such as physical vapor deposition (PVD), chemicalvapor deposition (CVD), atomic layer deposition (ALD), electrochemicaldeposition and/or molecular beam epitaxy may be used to form one or morematerials on the substrate.

Subsequently, portions of the one or more materials, and in someinstances, portions of the substrate, may be removed, such as by wetand/or dry etching, to form the features. In some examples, the featuresmay have high aspect ratios (e.g., ratio of height to width or diameter)and may be referred to as high-aspect-ratio (HAR) features. For example,the features might be separated from each other by HAR openings.

During processing, the substrate and the features may be subjected towet processing, such as wet cleaning, and subsequent drying. Forexample, wet cleaning can be helpful to remove residue left behind, suchas by the removal process or other processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents various examples of feature toppling.

FIGS. 2A-2D illustrate cross-sectional views of processing stepsassociated with forming a semiconductor device, in accordance with anumber of embodiments of the present disclosure.

FIG. 3 is a block diagram illustration of an apparatus formed, at leastin part, in accordance with a number of embodiments of the presentdisclosure.

FIG. 4 illustrates a processing apparatus that may be used inconjunction with processing disclosed herein, in accordance with anumber of embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure includes processing methods associated withforming semiconductor devices, such as integrated circuits, memorydevices MEMS, among others. A number of embodiments include methods,comprising: removing a material from a structure to form an opening inthe structure, exposing a residue resulting from removing the material,to an alcohol gas to form a volatile compound, and removing the volatilecompound by vaporization. The structure may be used in semiconductordevices, such as integrated circuits, memory devices, MEMS, amongothers.

Embodiments of the present disclosure provide benefits, such as reducingthe likelihood of feature collapse (e.g. toppling) during processingcompared to previous approaches. For instance, a number of embodimentsuse a (e.g., an all) dry-cleaning process (e.g., without using anyliquids) to remove the residue that remains after forming features usinga dry process, such as a dry etch, as opposed to using the wet cleaningprocesses of previous approaches. For example, forming a volatilecompound, such as a volatile solid, from the residue by exposing theresidue to the alcohol gas and removing the volatile compound byvaporization, such as by sublimation, is an example of an embodiment ofa dry-cleaning process.

Some prior approaches use a wet clean to dissolve and remove the residuefrom a structure resulting from forming features (e.g., using a dryetch). The structure is then dried (e.g., by exposing the structure to agas, such as nitrogen) to remove the liquids used during the wet clean.However, during drying, surfaces of the liquid in openings between thefeatures may come in contact with the gas, resulting in capillary forcesin the openings at an interface between the liquid and the gas that cancause the features to topple (e.g., collapse) toward each other,bringing adjacent features into contact with each other. For example,FIG. 1 illustrates a feature 101 toppling (e.g., collapsing) into anadjacent feature and a pair of adjacent features 102 toppling into eachother (e.g. in what is sometimes referred to as bridging), as a resultof the capillary forces in openings between the features caused by theliquid on and/or within the openings being in contact with the gas. Thiscan lead to defects in the semiconductor device, and can even render thesemiconductor device inoperable.

The disclosed embodiments eliminate wet cleaning and the associateddrying of previous approaches in favor of dry-cleaning processes thatconvert residues (e.g., left by dry etching) into volatile compounds,such as volatile solids, and that remove the compounds by vaporization,such as by sublimation. For instance, the disclosed dry-cleaningprocesses reduce the likelihood of (eliminate) the feature collapseassociated with wet cleaning of previous approaches.

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown, byway of illustration, specific examples. Other examples may be utilizedand structural and electrical changes may be made without departing fromthe scope of the present disclosure. The following detailed descriptionis, therefore, not to be taken in a limiting sense, and the scope of thepresent disclosure is defined only by the appended claims andequivalents thereof.

The term semiconductor can refer to, for example, a material, a wafer,or a substrate, and includes any base semiconductor structure.“Semiconductor” is to be understood as including silicon-on-sapphire(SOS) technology, silicon-on-insulator (SOI) technology,thin-film-transistor (TFT) technology, doped and undoped semiconductors,epitaxial layers of a silicon supported by a base semiconductorstructure, as well as other semiconductor structures. Furthermore, whenreference is made to a semiconductor in the following description,previous process steps may have been utilized to form regions/junctionsin the base semiconductor structure, and the term semiconductor caninclude the previously formed structures containing suchregions/junctions.

FIGS. 2A-2D illustrate cross-sectional views of processing stepsassociated with forming a semiconductor device, such as a portion of anintegrated circuit, a memory device, a MEMS, among others, in accordancewith a number of embodiments of the present disclosure. For example, theprocessing steps may be associated with forming (e.g., a memory arrayof) a DRAM memory device, a NAND flash memory device, a NOR flash memorydevice, among others.

FIG. 2A depicts a structure (e.g., to be used in a semiconductor device)after several processing steps have occurred. The structure may includea a base structure, such as a substrate 206 (e.g., a semiconductor). Insome examples, one or more materials 210, such as silicon-basedmaterials, may be formed on (e.g., over) a surface 208, such as an uppersurface, of substrate 206, using, for example, a deposition process,such as PVD, CVD, ALD, electrochemical deposition and/or molecular beamepitaxy.

Features 211, such as nanofeatures (e.g., having a width or diameter ofabout 0.1 nanometer to about 100 nanometer) are formed by removingportions of the structure, such as portions of the one or more materials210 and portions of substrate 206. The removal process forms openings212, such as spaces (e.g., trenches), through the one or more materials210, stopping on or in (e.g., as shown in FIG. 2A) substrate 206. Forexample, an opening 212 may be between adjacent features 211. In someexamples, each of the respective features 211 includes the one or morematerials 210 and a portion of substrate 206.

In some examples, portions of the openings 212 in substrate 206 (e.g.,below surface 208) may correspond to isolation regions, such as shallowtrench isolation (STI) regions. In an example, a feature 211 may beentirely of substrate 206, and openings 212 may correspond to STIregions. In other examples, features 211 may be the one or morematerials 210, such as silicon-based materials. For example, at least aportion of a memory cell, such as a non-volatile memory cell, may beformed from feature 211. For example, a feature may include materialsfor a memory cell, such as tunnel dielectric, a charge storage material,and a conductor (e.g., for control gate) for a memory cell. In someexamples, openings 212 may define memory cells on either side thereof(e.g., features may form memory cells). Features 211 may be HARfeatures, and openings 212 may be HAR openings. For example, an HAR mayhave a height to width or diameter ratio of 10 to 1 to 25 to 1 orgreater.

In some examples, openings 212, and thus the structure in FIG. 2A, maybe formed using dry processing, such as a dry removal process (e.g., adry etch). For example, a mask (not shown), such as imaging resist(e.g., photo-resist), may be formed over the one or more materials 210and patterned to expose regions of the one or more materials 210. Theexposed regions may be subsequently removed, such as by the dry etch, toform openings 212 that may terminate on or in substrate 206. In someexamples, the dry processing may be performed in chamber of a processingapparatus.

As shown in FIG. 2A, residues, such as etch residues 213, resulting fromremoving the portions of the one or more materials 210 resulting in thestructure in FIG. 2A, are left on sides and upper surfaces 216 offeatures 211 and on the bottoms of openings 212. In some examples,residues 213 may include non-volatile metals, such as aluminum ortitanium, among others, halides, such as non-volatile metal halides(e.g., aluminum fluoride), metal oxides, and silicon halides, amongothers. The presence of the metal may be due to the fact that thechamber in which the structure of FIG. 2A is formed may be fabricatedfrom the metal. For example, the chamber may contribute to the residuesduring the formation of features 211.

The presence of residues 213 could prevent proper formation ofsubsequent materials in openings 212 and on (e.g., over) surface 216.Therefore, a dry-cleaning (e.g., an all dry cleaning) process isimplemented to remove residues 213 in accordance with a number ofembodiments of the present disclosure. For example, the dry cleaningprocess may be performed in the chamber.

In some examples, the dry-cleaning process may include forming an (e.g.,anhydrous) alcohol gas, such as by vaporizing (e.g. anhydrous) methanol,ethanol, propanol, or the like (e.g., using an alcohol gas module). Thestructure of FIG. 2A may be exposed to the alcohol gas to exposeresidues 213 to the alcohol gas.

As shown in FIG. 2B, exposure of residues 213 to the alcohol gas formsresidual volatile materials 217, such as volatile compounds, in openings212 and on the upper surfaces 216 from residues 213 and the alcohol gas.For instance, the alcohol gas and residues may react to form volatilematerials 217. Volatile materials 217 may be comprised of metallicelements, such as metal alkoxide materials, aluminum alkoxide materials,aluminum trimethoxide materials, and the like. In some examples, thevolatile materials 217 may include volatile solids. In some instances,the alcohol gas may facilitate the removal of the silicon halides andmay form methoxy terminated surfaces on the side surfaces and uppersurfaces 216 of features 211 and on the bottoms of openings 212.

As shown in FIG. 2C, the dry-cleaning process includes removing volatilematerials 217 by vaporization to form the structure of FIG. 2C. In someexamples, volatile materials 217 may vaporize as soon as they are formed(e.g., immediately upon their formation). For example, volatilematerials 217 may vaporize (e.g., volatilize) while the residue isreacting with the alcohol gas (e.g., in the chamber). This may result inthe structure of FIG. 2C being formed directly from FIG. 2A. Forexample, the process may go directly from FIG. 2A to 2C. In suchexamples, the volatile materials 217 may form at a temperature andpressure at which the volatile materials 217 vaporize. For example, thetemperature and pressure of a chamber in which the reaction occurs maybe set to levels at which the volatile solid materials 217 vaporize.

In other examples, FIG. 2B may correspond to the reaction going tocompletion (e.g., the residue is done reacting with the alcohol gas).For instance, the structure of FIG. 2A may be exposed to the alcohol gasto produce the volatile materials 217 in FIG. 2B while at a temperatureand pressure at which volatile materials 217 do not vaporize. Forexample, residues 213 may be reacted with the alcohol gas at atemperature and pressure at which volatile materials 217 do notvaporize. Subsequently, the temperature and/or pressure (e.g., in achamber containing the structure of FIG. 2B) may be changed to levels atwhich volatile materials 217 vaporize. For example, after residues 213and the alcohol gas are done reacting, the temperature and/or pressuremay be changed so that volatile materials 217 vaporize. The vaporizationremoves volatile materials 217 to produce the structure of FIG. 2C fromthe structure of FIG. 2B.

In some examples, as shown in FIG. 2D, a material 222 (e.g., a solidmaterial) may be formed (e.g., at a deposition tool not shown) in theopenings 212 in the structure of FIG. 2C. For example, material 222 maybe formed in a gaseous phase or a plasma phase, such as by PVD, CVD,ALD, among others. For example, material 222 might be an epitaxialsilicon material or a dielectric material, such as silicon oxide orsilicon nitride. In some examples, material 222 may overfill openings212 and extend over the upper surfaces 216 of features 211.Subsequently, a portion of material 222 may be removed, such as bychemical mechanical planarization (CMP) so that upper surfaces 224 ofmaterial 222 are coplanar with upper surfaces 216, as shown in FIG. 2D.In some examples, features 211 may form memory cells, such asnon-volatile memory cells.

FIG. 3 is a block diagram of an apparatus, such as a memory device 350.For example, memory device 350 may be a volatile memory device, such asa DRAM, a non-volatile memory device, such as NAND flash or NOR flash,among others. For example, memory device 350 may be formed, at least inpart, using the processing previously described, such as in conjunctionwith FIGS. 2A-2D.

Memory device 350 includes a controller 352, such as an applicationspecific integrated circuit (ASIC), coupled to a memory array 354, suchas a DRAM array, a NAND array, a NOR array, among others. For example,memory array 354 might be formed, at least in part, according to theprocessing described previously.

The controller 352 can control the operations on the memory device 350,and of the memory array 354, including data sensing (e.g., reading) anddata programming (e.g., writing), for example. Memory device 350 may becoupled to a host device (not shown in FIG. 3 ).

FIG. 4 illustrates a processing apparatus 460, such as a fabricationapparatus, that may be used in conjunction with processing associatedwith forming a semiconductor device, in accordance with a number ofembodiments of the present disclosure. Processing apparatus 460 includesa chamber 462 (e.g., in which dry processing may be performed). In someexamples the structure of FIG. 2A may be formed in chamber 462.Temperature controller 464 and pressure controller 466 are respectivelyused to control the temperature and pressure in chamber 462. Alcohol gasmay be formed and supplied to chamber 462 using alcohol gas module 468.For example, the residue may react with the alcohol gas in chamber 462.A purge module 470 may be used to purge gasses from chamber 462.

Embodiments of the disclosure use a dry-cleaning process to cleanresidue (e.g., resulting from dry removal process, such as a dry etch).For example, a dry-cleaning process may involve exposing the residue toan alcohol gas to form a volatile compound, such as a volatile solid,and removing the compound by vaporization, such as by sublimation. Thedisclosed dry-cleaning processes avoid the wet-cleaning and subsequentdrying processes, and thus the resulting feature collapses, of previousapproaches.

Although specific examples have been illustrated and described herein,those of ordinary skill in the art will appreciate that an arrangementcalculated to achieve the same results may be substituted for thespecific embodiments shown. This disclosure is intended to coveradaptations or variations of one or more embodiments of the presentdisclosure. It is to be understood that the above description has beenmade in an illustrative fashion, and not a restrictive one. The scope ofone or more examples of the present disclosure should be determined withreference to the appended claims, along with the full range ofequivalents to which such claims are entitled.

What is claimed is:
 1. A method of forming a semiconductor device,comprising: forming a plurality of features in a structure; reacting aresidue, resulting from forming the plurality of features, with analcohol gas to form a metal alkoxide material at a temperature andpressure at which the metal alkoxide material does not vaporize; andremoving the metal alkoxide material by vaporization.
 2. The method ofclaim 1, wherein removing the compound by vaporization comprisesvaporizing the metal alkoxide material after the residue is donereacting with the alcohol gas.
 3. The method of claim 2, whereinvaporizing the metal alkoxide material after the residue is donereacting with the alcohol gas comprises sublimation.
 4. The method ofclaim 1, wherein the plurality of features are high aspect ratiofeatures.
 5. The method of claim 1, wherein the metal alkoxide materialan aluminum alkoxide material.
 6. The method of claim 1, wherein theresidue comprises silicon halides.
 7. The method of claim 1, wherein theresidue comprises aluminum halides.
 8. The method of claim 1, furthercomprising forming the plurality of features using a dry process.
 9. Amethod of forming a semiconductor device, comprising: forming aplurality of features in a silicon-based structure; reacting a residue,resulting from forming the features, with an alcohol gas to form a metalalkoxide material at a temperature and pressure at which the metalalkoxide material does not vaporize; removing the metal alkoxidematerial; and forming a dielectric material in spaces between thefeatures.
 10. The method of claim 9, further comprising changing thetemperature and/or pressure after the residue and the alcohol gas aredone reacting so that the metal alkoxide material vaporizes.
 11. Themethod of claim 9, wherein forming the plurality of features in asilicon-based structure comprises forming support pillars for a memorycell.
 12. The method of claim 9, wherein the alcohol gas is methanol.13. The method of claim 9, wherein forming the dielectric material inspaces between the features comprises forming an isolation region.
 14. Amethod of forming a semiconductor device, comprising: removing amaterial from a structure to form an opening in the structure; exposinga residue, resulting from removing the material, to an alcohol gas toform aluminum trimethoxide at a temperature and pressure at which thealuminum trimethoxide does not vaporize; forming methoxy terminatedsurfaces, from the exposure of the residue and the alcohol gas, on thestructure; and removing the aluminum trimethoxide by vaporization afterthe residue and the alcohol are done reacting.
 15. The method of claim14, wherein removing the aluminum trimethoxide by vaporization comprisesreacting the residue with the alcohol gas at a temperature and pressuredifferent from the temperature and pressure at which the aluminumtrimethoxide is formed.
 16. The method of claim 14, wherein removing thealuminum trimethoxide from the structure comprises a dry removalprocess.
 17. The method of claim 14, wherein the alcohol gas isanhydrous alcohol.